Low-Temperature, Efficient Synthesis of Highly Crystalline Urchin-like Tantalum Diboride Nanoflowers.

Urchin-like tantalum diboride (TaB2) nanoflowers were successfully synthesized via a high-efficiency and energy-saving methodology, molten-salt and microwave co-modified boro/carbothermal reduction, using less expensive B4C as a reducing agent. By taking advantage of the synergistic effects of the molten-salt medium and microwave heating conditions, the onset formation temperature of TaB2 was drastically reduced to below 1000 °C, and phase-pure powders of TaB2 nanoflowers were obtained at temperatures as low as 1200 °C within only 20 min. Notably, the present temperature conditions were remarkably milder than those (>1500 °C for several hours) required by conventional reduction methods, which use the strong, but expensive, reducing agent, elemental boron. The resulting urchin-like TaB2 nanoflowers consisted of numerous uniform single-crystalline nanowires with lengths up to 4.16 μm, and high aspect ratios >10. This result indicated that the as-synthesized urchin-like TaB2 nanoflowers possessed high specific surface area and anisotropic morphology, which were favorable not only for sintering, but also for toughening their bulk counterparts.